'\" et
.TH SEEKDIR "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
seekdir
\(em set the position of a directory stream
.SH SYNOPSIS
.LP
.nf
#include <dirent.h>
.P
void seekdir(DIR *\fIdirp\fP, long \fIloc\fP);
.fi
.SH DESCRIPTION
The
\fIseekdir\fR()
function shall set the position of the next
\fIreaddir\fR()
operation on the directory stream specified by
.IR dirp
to the position specified by
.IR loc .
The value of
.IR loc
should have been returned from an earlier call to
\fItelldir\fR()
using the same directory stream. The new position reverts to the one
associated with the directory stream when
\fItelldir\fR()
was performed.
.P
If the value of
.IR loc
was not obtained from an earlier call to
\fItelldir\fR(),
or if a call to
\fIrewinddir\fR()
occurred between the call to
\fItelldir\fR()
and the call to
\fIseekdir\fR(),
the results of subsequent calls to
\fIreaddir\fR()
are unspecified.
.SH "RETURN VALUE"
The
\fIseekdir\fR()
function shall not return a value.
.SH ERRORS
No errors are defined.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
The original standard developers perceived that there were restrictions
on the use of the
\fIseekdir\fR()
and
\fItelldir\fR()
functions related to implementation details, and for that reason these
functions need not be supported on all POSIX-conforming systems. They
are required on implementations supporting the XSI option.
.P
One of the perceived problems of implementation is that returning to a
given point in a directory is quite difficult to describe formally, in
spite of its intuitive appeal, when systems that use B-trees, hashing
functions, or other similar mechanisms to order their directories are
considered. The definition of
\fIseekdir\fR()
and
\fItelldir\fR()
does not specify whether, when using these interfaces, a given
directory entry will be seen at all, or more than once.
.P
On systems not supporting these functions, their capability can
sometimes be accomplished by saving a filename found by
\fIreaddir\fR()
and later using
\fIrewinddir\fR()
and a loop on
\fIreaddir\fR()
to relocate the position from which the filename was saved.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIfdopendir\fR\^(\|)",
.IR "\fIreaddir\fR\^(\|)",
.IR "\fItelldir\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<dirent.h>\fP",
.IR "\fB<sys_types.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
